Contact construction with metallic contact members and auxiliary metallic arc suppressant conducting members



. J. GRIBBLE 3,166,660

Jan. 19, 1965 J CONTACT CONSTRUCTION WITH METALLIC CONTACT MEMBERS ANDAUXILIARY METALLIC ARC SUPPRESSORS CONDUCTING MEMBERS Filed May 9. 1960IN VEN TOR. JOSEPH J 62/55: 5

United States Patent Ofitice Patented Jan. 19, 1965 This inventionrelates to an electrical contact device and more particularly to anelectrical contact device employing special contacts in a' relationwhich provides a more effective self-contained, arc-extinguishing means.

One of the most persistent problems encountered in the use of electricalcontacts is the excessive and premature pitting and erosion of suchcontacts by the arcing which occurs between the contacts as a circuit ismade or broken. Because of this arcing, the contacts must be replacedfrequently, thereby involving considerable expense in timejandmaterials.

It is an object of the present invention to provide electrical contactswhich are much less subject to pitting, burning and erosion by arcingand which have a substantially longer life than that of prior contacts.

A further object'of the invention is' to provide electrical contactsthat extinguish the arc and resist welding more efficiently than that ofprior constructions.

A further'object of the invention is toprovide an electrical contactconstruction which is economical to manufacture andthat is eflicient andtrouble-free in use, and in which the specific contacts arearranged in arelation to the arc path so that the arc is moved efiieiently to theextinguishing position, I

Briefly, the foregoing objects-are accomplished by the provisionof an,electrical contact construction including a pair of opposed coactingcontacts, each of said contacts having a contiguous auxiliary arereceiving conductor and each main contact andits auxiliary conductorbeing mounted, respectively, adjacent the outer free, parallel-spacedend portions of an electrical conducting bar.

The contacts are oppositely spaced in face to face relation and areadapted for movement into and out of conlariy resistant to weldingbecause of its high melting point. The auxiliary conductors are formedof a semi-refractory composition such as silver cadmium oxide, which isan arc-suppressant material of high interrupting capacity. Thus, themagnetic field created by the current flowing through the contactscauses the arc to travel'from the partially spaced weld-resistantcontacts to the substantially spaced arc-suppressant, auxiliaryconductors where the arc is interrupted. With this construction, anelectrical contact device is provided having self-contained arcxtinguishing means, such contact device being of unusually simpleconstruction and having a substantially longer life than that of priorconstructions.

Other objects and advantages of the invention will become apparent fromthe following description taken in conjunction with thedrawings,.wherein:

FIG. 1 is a perspective view of an electrical contact device constructedin accordance with the invention, with tact device shown in FIG. 1, thedevice being shown in closed position.

Referring to the drawings, there, is shown an electrical contact deviceA of the invention and comprising the contact supporting means in theform of two spaced electrical load current conducting bars 10 and 12having parallel outer end portions, the outer end portions havingcoacting, oppositely disposed, contacts or contact members 14 and 16,respectively, supported fixedly thereon in face to face relation. Thecontact 14 has a con tiguous auxiliary conductor 18 and the contact 16has a contiguous auxiliary conductor 20. Y

The conducting bars 10 and 12 areadapted'for movement toward and awayfrom eachaother in any well known manner, whereby, the contacts 14 and.16 move into and out of engagement with each other for making andbreaking an electric circuit. For. illustration, the bar 12 is shown asstationary and the bar 10 is movable about a I pivot 13 toward and awayfrom thebar 12.

tact with each other for making and breaking an elec- 5 trical circuit.The auxiliary conductors are disposed also in spaced, face to facerelation, but do not come into contact with each other when the contactsare in either open or closed position. More specifically, each contactand its contiguous auxiliary conductor present a stepped construction,in side elevational view, with the distance between the contacts beingless than the distance between the contiguous'auxiliary conductors.

In operation, with the contacts in engagement with each other, electricload current flows in through one of the conducting bars, through theengaged contacts and creates a magnetic field ,having a resultant forcedirected outwardly towards the free ends of the conducting bars. Uponopening of the contacts, if an arc is created, it acts 1 Furthermore,contacts 'aref formedoffa renac'toryeom.

thence through the other conductorbarf Thiscurrent I f position'such' astungstencarbideimpregnated with silver, such'material being haidandothigh strjength andparticu- The auxiliary conductors 18 and 20 aredisposed in spaced, face to face relation a greater distance apart thanthe contacts 14 and 16 so that they do not come into contact with eachother even when the'contacts 14 and 16 are in closed position. Thus thecontacts and conductors present a stepped construction.

1 In operation, with the contact members i-t and 16 in engagement witheach other, as shown in FIG. 4, electric current, flows, for example,through the conducting bar 10,

' down through the engaged contacts 14 and. 16, and thence throughtheiconducting bar 12, as shown by the arrows 17. This current flowcreates a magnetic field having a resultant force which is directedoutwardly, to the right in FIG. 4, toward the free ends of the bars 10and 12, as indicated by the arrow 21; When the contacts 14 and 16 areparted, as shown in FIG. 1, an arc is formed between the contacts andthe magnetic field, causes the arc to travel from the contacts to theauxiliary conductors 13 'j f 'and 2i? wherethe arc is broken, such areprogression ber "ingrepresented by the broken lines 22. Thusthe conf'ductors-lfi and '20 are arranged in. parallel spaced relation along thenormal path of the are. This path is in a direction to 'the right; inFIG, 4, and is unobstructed fora. 7

distance outwardly beyond the conductors 18 and 2Q sufiij j'cientltopermit interruption' of the arc. a. Thecontacts 14 and {Glare formed ofa refractory conrposition, such as a matrix oftungstencarbideimpregnated with silver; This composition is hard 1 and of high strengthand resistant-to arc erosion and wear, yet'is a j good conductor ofelectricity. In the preferred form, such composition consists of about50% tungsten carbide and about 50% silver, both by volume. However,these percentages may be varied somewhat. For example, tugsten carbidemay be from about 40% to 60%, and the silvermay provide the balance.

The contiguous auxiliary conductors are formed of a semi-refractorymaterial, such as silver cadmium oxide. This composition is highlyarc-suppressant and has a high interrupting capacity. In the preferredform, such composition consists of about 85% silver and about 15%cadmium oxide, both by volume. The percentages may be varied. Forexample, the silver may range from about 80% to 90% and the cadmiumoxide may provide thebalance.

Having thus described my invention, I claim:

1. A contact construction comprising a pairof elongated load currentconducting bars extending lengthwise alongside each other in face toface spaced relation from each other transversely of their lengths andmovable transversely of their length toward and away from each other sothat the load current path therein is endwise of the bars, metalliccontact members on the adjacent faces of the bars, respectively, nearto, but spaced from, one end of the pair, and supported by the bars inspaced face to face relation, and movable by the bars into contact witheach other upon movement of the bars transversely of their length towardeach other, whereby, upon establishment of an are between the memberswhen they are moved apart, a magnetic field is established by the loadcurrent which forces the arc to travel from between the contact membersendwise of the bars towards and beyond said one end of the pair of bars,auxiliary conducting members of highly arc suppressant metallic materialmounted on the bars, respectively, outwardly from the contact memberstoward said one end of the pair and arranged so that they extenddirectly from the adjacent outer ends of the contact members,respectively, outwardly toward said end of the pair of bars, and are inspaced face to face relation to each other in the direction ofseparation of the contact members in all positions of the contactmembers, means supporting the bars so that the direct path of travel ofthe are from between the contact members under the influence of themagnetic field created by the load current, outwardly endwise of thebars past said one end of the pair, is unobstructed, endwise of thebars, outwardly from the contact members, past said auxiliary membersand therebeyond a distance suflicient to permit interruption of the arcwhile it is substantially unconstrained endwise and laterally of thebars, said metallic contact members being of material of high electricalconductivity and high resistance to welding, wear, and are erosion, andsaid auxiliary conducting members being of metallic material of high arcinterrupting capacity.

2. The structure according to claim 1 wherein said contact portion isformed of tungsten carbide impregnated With silver.

3. The structure according to claim 2 wherein said tungsten carbide ispresent in an amount of about and silver is present in an amount ofabout 50%, by volume.

4. The structure according to claim 1 wherein said auxiliary portion isformed of silver cadmium oxide composition.

5. The structure according to claim 4 wherein said silver is present inan amount of about 85% and the cadmium oxide is present in an amount ofabout 15 by volume.

6. The structure according to claim 1 wherein said contact portion isformed of a material consisting of about 50% tungsten carbide and about50% silver, and said auxiliary portion is formed of a materialconsisting of about 85% silver and about 15% cadmium oxide, by volume.

7. The structure according to claim 1 wherein said contact members areformed of a material consisting of about 40% to tungsten carbide andfrom about 60% to 40% silver, both by volume, and said auxiliary membersare formed of a material consisting of about to silver and from about20% to 10% cadmium oxide, both by volume.

References Cited in the file of this patent UNITED STATES PATENTS UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,166,660January 19, 1965 Joseph J. Gribble It is hereby certified that errorappears in the above numbered patent requiring correction and that thesaid Letters Patent should read as corrected below.

Column 4, after line 43, insert the following:

2,289,708 Jackson July 14, 1942 2,307,668 Cox Jan. 5, 194

2,360,522 Shobert 11 et a1. Oct. 17, 1944 2,506,991 Brown May 9, 19502,730,594 Page -Jan. 10, 1956 2,890,315 Graves, Jr. -June 9, 1959 Signedand sealed this 24th day of August 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

1. A CONTACT CONSTRUCTION COMPRISING A PAIR OF ELONGATED LOAD CURRENTCONDUCTING BARS EXTENDING LENGTHWISE ALONGSIDE EACH OTHER IN FACE TOFACE SPACED RELATION FROM EACH OTHER TRANSVERSELY OF THEIR LENGTHS ANDMOVABLE TRANSVERSELY OF THEIR LENGTH TOWARD ANS AWAY FROM EACH OTHER SOTHAT THE LOAD CURRENT PATH THEREIN IS ENDWISE OF THE BARS, METALLICCONTACT MEMBERS ON THE ADJACENT FACES OF THE BARS, RESPECTIVELY, NEARTO, BUT SPACED FROM, ONE END OF THE PAIR, AND SUPPORTED BY THE BARS INSPACED FACE TO FACE RELATION, AND MOVABLE BY THE BARS INTO CONTACT WITHEACH OTHER UPON MOVEMENT OF THE BARS TRANSVERSELY OF THEIR LENGTH TOWARDEACH OTHER, WHEEREBY, UPON ESTABLISHMENT OF AN ARC BETWEEN THE MEMBERSWHEN THEY ARE MOVED APRAT, A MAGNETIC FIELD IS ESTABLISHED BY THE LOADCURRENT WHICH FORCES THE ARC TO TRAVEL FROM BETWEEN THE CONTACT MEMBERSENDWISE OF THE BARS TOWARDS AND BEYOND SAID ONE END OF THE PARI OF BARS,AUXILIARY CONDUCTING MEMBERS OF HIGHLY ARC SUPPRESSANT METALLIC MATERIALMOUNTED ON THE BARS, RESPECTIVELY, OUTWARDLY FROM THE CONTACT MEMBERSTOWARD SAID ONE END OF THE PAIR AND ARRANGED SO THAT THEY EXTENDDIRECTLY FROM THE ADJACENT OUTER ENDS OF THE CONTACT MEMBERS,RESPECTIVELY, OUTWARDLY TOWARD SAID END OF THE PAIR OF BARS, AND ARE INSPACED FACE TO FACE RELATION TO EACH OTHER IN THE DIRECTION OFSEPARATION OF THE CONTACT MEMBERS IN ALL POSITIONS OF THE CONTACTMEMBERS, MEANS SUPPORTING THE BARS SO THAT THE DIRECT PATH OF TRAVEL OFTHE ARC FROM BETWEEN THE CONTACT MEMBERS UNDER THE INFLUENCE OF THEMAGNETIC FIELD CREATED BY THE LOAD CURRENT, OUTWARDLY ENDWISE OF THEBARS PAST SAID ONE END OF THE PAIR, IS UNOBSTRUCTED, ENDWISE OF THEBARS, OUTWARDLY FROM THE CONTACT MEMBERS, PAST SAID AUXILIARY MEMBERSAND THEREBEYOND A DISTANCE SUFFICIENT TO PERMIT INTERRUPTION OF THE ARCWHILE IT IS SUBSTANTIALLY UNCONSTRAINED ENDWISE AND LATERALLY OF THEBARS, SAID METALLIC CONTACT MEMBERS BEING OF MATERIAL OF HIGH ELECTRICALCONDUCTIVITY AND HIGH RESISTANCE TO WELDING, WEAR, AND ARC EROSION, ANDSAID AUXILIARY CONDUCTING MEMBERS BEING OF METALLIC MATERIAL OF HIGH ARCINTERRUPTING CAPACITY.